Many ion-generating devices that utilize a discharge phenomenon have been commercialized. These ion-generating devices are generally configured with an ion-generating element for generating ions, a high-voltage transformer for supplying a high voltage to the ion-generating element, a high voltage-generating circuit for driving the high-voltage transformer, and a power supply input unit such as a connector.
An example of the commercialized ion-generating elements includes the one that uses a metal wire, a metal plate having an acute-angled portion, a needle-like metal, or the like as a discharge electrode, and uses a metal plate, a grid, or the like at a ground potential as an induction electrode (counter electrode), or the one that uses the ground as an induction electrode and does not particularly dispose an induction electrode. In the ion-generating element of this type, the air serves as an insulator. This ion-generating element utilizes a scheme to produce a discharge phenomenon by causing electric field concentration at a tip of an electrode, which has as an acute-angled portion such as a needle-like portion to serve as a discharge electrode, when applying a high voltage to the electrode, and causing an electrical breakdown of the air in close vicinity of the tip.
An example of the ion-generating elements that utilize this scheme is a device disclosed in, for example, Japanese Patent Laying-Open No. 10-199653. This publication discloses a device which includes a discharge electrode provided with a needle-like metal, and a flat-plate electrode with a hole, provided to face the discharge electrode, and serves for extracting negative ions generated as corona discharge occurs, to an outside of the device.
Another example is a device disclosed in, for example, Japanese Patent Laying-Open No. 8-255668. This publication discloses a device which has a positive discharge electrode, a negative discharge electrode, and a ground electrode adjacent to both of the discharge electrodes, and serves for emitting both of positive ions and negative ions to an outside of the ion-producing device.
Still another example is a device disclosed in, for example, Japanese Patent Laying-Open No. 2002-374670. This publication discloses an ion-generating device of the type provided with an ion-generating electrode serving as a discharge electrode and not provided with an induction electrode.